The UI initiation sequence has 4 steps.
The problem I am having is that step 3 (where the user should enter his IP address) never comes up, the process goes straight from step 2 to step 4.
Consequence is that after hitting the start button in step 4, the process ends up in the step that handles “Trouble Connecting”.
I could not find the script that handles these steps.

If you use the latest build (http://trinusvr.com/server/trinus.unitypackage), the TrinusUI prefab includes an array where the intro pages are set, to be shown sequentially. You can add or remove pages there. The IP address page in that version was removed, in favour of just giving the option at the connection stage. You can add the IP page again if desired.